PHYSIOLOGY AND MORPHOLOGY OF CALIFORNIA HEPATIC^ 33 



any consequence fell on the twenty-first of August, but liver- 

 worts barely revived by it were overtaken by a period of dry, 

 hot weather which lasted till September 23, when the rainy 

 season began. It might justly be assumed that the resumption 

 of growth, as regards Fossomhronia at least, began at this time, 

 More than the usual amount of rain was recorded for October 

 and November and growing conditions were very favorable. 

 Material collected in early February showed sporongia in which 

 the spore-mother cells w^ere preparing to pass into the tetraspore 

 condition, and six weeks later material was collected bearing 

 ripe spores and elaters. From this it will be seen that, having 

 a favorable rainy season, the time required to produce ripe 

 spores is approximately six months after the first rains of any 

 consequence. Judging from the advanced development in which 

 one finds antheridia and archegonia at the close of the summer 

 season, fertilization must occur within a few weeks after 

 resumption of growth is well established. 



With regard to the plants that had grown unchecked through- 

 out the summer, it must be noted that temperature and humidity 

 conditions are widely different from those prevailing in winter. 

 Though the plants were well irrigated, the atmospheric condi- 

 tions were such as to influence to some extent the growth and 

 behavior of the thallus and fruiting organs. Assuming, how- 

 ever, the same rate of development of the sporogonia for these 

 plants as for those grown in winter, fertilization must have 

 occurred during July and later. Growing in a paraffin-coated 

 glass dish containing Knop's nutrient solution, the writer has 

 under observation several plants of Fossonibronia^ placed there 

 a month ago in air-dry condition as nearly free from soil parti- 

 cles as they could be rendered by the use of a fine, stiff brush. 

 Antheridia and archegonia then in the initial stages of develop- 

 ment are now about as far advanced as were the oldest of those 

 observed as soon as the plants had revived — in the course of 

 twelve hours. These oldest ones are now maturing. It will 

 be shown elsewhere, however, that Knop's solution affords a 

 very active stimulus to development of the thallus and fruiting 

 organs, probably shortening the time of their normal develop- 

 ment considerably. 



Proc. Wash. Acad. Sci., January, 1908. 



